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Likewise, Fletcher Building topped the list for the unders after reporting a net loss of $190m following on from a string of earnings downgrades.

Fund managers were nevertheless encouraged by Fletcher's announcement in late December that it had sold its US unit, Formica, for $1.2 billion.

Some see that as a long-awaited turning point for what was once one of the market's mainstays.

Shane Solly, portfolio manager, Harbour Asset Management

Unders:

Solly said that Fletcher Building and Metro Performance Glass were two businesses that highlighted the challenges facing the building industry, including the way in which construction contracts are set.

"Z Energy and Sky TV are good reminders that companies need to keep looking after their customers and not take them for granted, or they risk regulatory pressure and loss of customers," Solly said.

"Not total surprises to us but companies that have delivered on strategy earlier and better than we may have expected.

"All four businesses are showing attractive long-term structural growth potential that may be less dependent on economic activity than some other businesses," Solly said.

Aside from the headline-grabbing winners, Solly said the utilities - the big power generators/retailers - and the property companies, had done a good job protecting investors' capital.

"We always point to the growth businesses, but there is an undertone of undersung heroes who have actually done very well for investors," Solly said.

"Fletcher Building has been disappointing, but we are seeing glimmers of improvement there.

"At the operating level, there are is certainly a tail of things to work through and that will take time," he said.

Josh Wilson, senior portfolio manager, NZ Funds

Unders:

"Despite low expectations, Fletcher Building has managed to consistently disappoint, from the final kitchen-sinking of construction losses in February to the recent downbeat earnings guidance."

Wilson said the Formica sale could be Fletcher Building's first step along the path to investor redemption.

"Z Energy's half-year results in November were a big disappointment for shareholders. The company downgraded earnings expectations and backed away from their much-touted dividend policy - a kick in the teeth for shareholders already suffering from the threat of government intervention in the fuel market and a refinery outage earlier in the year."

Michael Hill's first quarter sales update in October came as a big surprise for the market, Wilson said.

The decision to move away from their previous highly promotional approach was both poorly communicated and executed, and saw sales drop significantly.

The share price fell 24 per cent on the day of the announcement.

Overs:

"It feels a long time ago now but in our view, a2 Milk takes the prize for the biggest upside surprise with its half-year results announcement in February," Wilson said.

"Not only did they announce growth well ahead of market expectations, but also a comprehensive strategic partnership with Fonterra – a tacit admission from the incumbent that a2 Milk, both the product and the company, is the real deal and could no longer be ignored.

"The share price rose 39 per cent over the following two days, adding $2.7b to the company's value."

Takeover target Trade Me's full-year results in August highlighted the company's growth potential and strong execution in spite of increasing competition from tech behemoths like Facebook and Amazon.

"This clearly caught the eye of private equity investors."

Daniel Kieser, managing director, Shareclarity

Outside the big names, those stocks further down in the scale of things have had their ups and downs.

Gentrack's revenue growth slowed in 2018 and management expects it will slow further in 2019, despite its recent acquisition of Evolve Analytics in the United Kingdom.

"Gentrack's focus on Europe hasn't been helped by Brexit and new pricing regulations that could affect some of its larger customers, the energy retailers," Kieser said.

Kieser also named Green Cross Health, whose market share could be under threat from the Chemist Warehouse, the aggressive Australian discount retailer who entered the New Zealand market late last year.

Green Cross Health is focusing on a "personalised" in-store experience, he said.

"Whether customers favour it over lower prices is still to be seen," Kieser said.

Overs:

Mobile phone software company, Plexure, which posted its first positive top-line earnings in a long time.

"It's still early, but Plexure seems to have curtailed some of its costs and is showing good growth in Europe and Asia," Kieser said.

Skellerup showed positive signs across its business, most notably its improving inventory management, its North American revenue growth and its margin expansion, he said.

Hallenstein Glasson delivered one of the better results, particularly from its Australian Glassons stores, according to Kieser.

Stephen Bennie, fund manager, Castle Point Funds

Unders:

"This year's losers are frankly not that much of a surprise," he said.

He also said that Sky TV's and NZME's business models had come under pressure.

"Agricultural companies will always make a list of winners and losers, given the often volatile nature of their earnings, and bottom of that pile this year was Comvita which really stung investors," Bennie said.

The December takeover bid by Apax Partners will see Trade Me finish around 40 per cent up for the year.

"A good trading update at its full-year result in August had seen the company drift into the top half of the draw but the real juice was the takeover bid that came in at a premium of 26 per cent to the previous last trade."

Mark Lister, head of private wealth research at Craigs Investment Partners

Unders:

Like other commentators, Lister was downbeat on Fletcher Building, whose shares fell 30 per cent in 2018 after already losing a third of their value in 2017.

"Over the past decade Fletcher Building has returned less than term deposits, and if dividends are excluded they've gone backwards," he said.

"It remains one of our biggest companies and we all want to see it succeed."

Lister said that Metro also had a terrible year and fell more than 40 per cent to record lows.

A range of factors was to blame, including operational issues and increasing competition.

As the economic cycle enters a relatively late phase, it's a long road back to the $1.70 IPO price, he said.

Overs:

Lister said it was hard not to include a2 Milk in a list like this.

A2 shares were up more than 30 per cent in 2018 as the company more than doubled its net profit on the back of healthy infant formula sales into China.

There were a few hiccups around the chief executive transition, while the regulatory environment in 2019 presents some challenges.

However, so far the company has delivered and shareholders have been handsomely rewarded, Lister said.

Trade Me shares returned a stunning 43 per cent, and it wasn't solely because of a takeover bid emerging, he said.

"Earnings growth was better than expected, the property division returned to form and shareholders were paid a very healthy special dividend.

"The takeover news was the icing on the cake, although it'll be sad to lose one of our great businesses from the market.

Lister saw EBOS Group as a quiet achiever - posting a 15 per cent gain in 2018, on the back of astute acquisitions and sensible management.

"EBOS has been one of the most underrated companies on the NZX during the last decade, but one of the best performers.

"The shares have returned 26 per cent per annum over the last ten years, more than double the NZX 50 return over the same period. Very few companies have bettered that, and none have done so with such consistency."

Mark Brown, chief investment officer Devon Funds Management

Unders:

"Fletcher Building has been disappointing, but Formica's sale will put Fletcher Building in a good position."

Z Energy cut its full-year earnings guidance after rising oil prices and a weaker New Zealand dollar slashed its first-half operating profit by 21 per cent.

A Commerce Commission inquiry into petrol prices in 2019 may also weigh on the stock, Brown said.

Overs:

Trade Me surpassed everyone's expectations, Brown said.

"Prior to that, they paid a special dividend, which led to a significant re-rating of the share."

Brown said Vista - which has re-entered the NZX50 index - was another one to surprise on the upside.

"It's now a $600 million market cap stock and one of New Zealand's pre-eminent global IT businesses that actually produces cash profits," he said.